The president of the opposition Christian Democratic Party and two other party leaders were ordered jailed by a Chilean judge today for seeking to organize a national protest against the government of Gen. Augusto Pinochet next week.

Gabriel Valdes, who was foreign minister in the late 1960s; Jose de Gregorio, the party's secretary general, and Jorge Lavandero, a former senator, were ordered detained on suspicion of involvement in the distribution of pamphlets calling for the protest Tuesday.

It was the first time during three months of growing confrontation between the Pinochet government and its opposition that political party leaders were jailed. Chile's opposition parties have been officially dissolved by the military authorities and political activity is banned, but they have resumed organizational efforts and operate informally.

The detentions followed the arrest Monday of two Christian Democratic youth leaders and reflected an aggressive government effort to prevent another protest.

The centrist Christian Democratic Party has taken the lead in organizing what would be the third national protest against military rule in the last three months. Last month's, called by opposition labor leaders, led to massive demonstrations and touched off a series of strikes by labor unions.

Since then President Pinochet, whose political position has appeared to be increasingly threatened by the unrest, has declared that no more protests will be allowed. Government authorities have jailed, internally exiled or brought court charges against more than two dozen labor leaders and initiated a crackdown on the news media that has all but halted reports of strikes and protests.

Today's action, announced to reporters by the attorney for the Interior Ministry, appeared to signal the government's intent to adopt an equally hard line against political party leaders, who have taken over active leadership of the protest movement from the hard-pressed labor unions.

"This is an arbitrary action that is too compliant with the wishes of the government," said Patricio Alwyn, a former senator and Christian Democratic leader, of today's court action. He said the judge's ruling would be appealed on Monday.

Valdes, de Gregorio and Lavandero were called to court to testify in the case of the two youth leaders arrested with 700,000 pamphlets promoting Tuesday's protest. Under the terms of their detention they are to be held in the Santiago public jail and not allowed visitors for up to five days, when the judge, Arnoldo Dreyes, must decide whether to indict them or release them.

Party leaders said today it was likely the three men probably would be held until after Tuesday's planned demonstration. However, they said they hoped that detention would increase momentum for the protest by galvanizing moderate sectors into action.

Sources said that directors of the Christian Democratic Party met last night to decide how to respond to the court summons today, and more militant leaders argued that Valdes should openly take responsibility for the protest and force the court to jail him.

Ironically, the party leadership decided against such action only to have the judge order the detention anyway.

Valdes, 64, who was named president of the Christian Democrats a little over a year ago, had denounced what he described as a government campaign to "foment hatred and fear" in a press conference earlier this week. He said that thousands of leaflets describing him as a "traitor" had been distributed across Chile and that he had been personally threatened.